Meanwhile, Senators John McCain and Lindsey Graham congratulated law enforcement on the arrest of the Boston Marathon bombing suspect and noted that the incident should be prosecuted as a terror case. The "perpetrators of these acts were not common criminals attempting to profit from a criminal enterprise, but terrorist trying to injure, maim, and kill innocent Americans," the senators said.

"Under the Law of War we can hold this suspect as a potential enemy combatant not entitled to Miranda warnings or the appointment of counsel."

[Updated 10:11 p.m. ET] "We've closed an important chapter in this tragedy," President Barack Obama said at the conclusion of the Boston Marathon bombing manhunt on Friday night.

But how did law enforcement find suspect Tsarnaev? A Watertown resident saw blood on a boat in his neighbor's backyard, Davis said.

"He opened the tarp and saw a man covered in blood," he said. The man retreated and alerted law enforcement.

Despite being bloody, the suspect exchanged gunfire with authorities from his hiding place, Davis said. Tsarnaev did not have explosives on him at the time of capture, according to Davis.

[Updated 9:41 p.m. ET] Massachusetts is celebrating the collaborative efforts of law enforcement, the public and the media in leading to the capture of the suspect in the Boston Marathon bombings.

"We're so grateful to bring justice and closure to this case," Massachusetts State Police spokesman Col. Timothy Alben said at a news conference in Watertown less than an hour after the capture of suspect Dzhokar Tsarnaev. "We're exhausted, folks, but we have a victory here tonight."

Gov. Patrick Deval praised local, state and federal agencies "who brought their A-game" along with members of the public "for their patience and participation in the case."

[Updated 8:59 p.m. ET] Law enforcement officials erupted in cheers in Watertown, Masssachusetts, on Friday night moments before Boston police tweeted that the remaining suspect in the Boston Marathon bombings was in custody.

CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody.

[Updated 8:44 p.m. ET] Law enforcement officials repeatedly appealed for surrender by a person believed to be Dzhokar Tsarnaev, the suspect in this week's Boston Marathon bombings, who was inside a boat in the backyard of a house in Watertown, Massachusetts, according to CNN staff at the scene. Among other things, they said, "We know you're in there" and "Come out with your hands up."

[Updated 8:39 p.m. ET] The FBI took two males and a female into custody for questioning Friday evening at New Bedford, Massachusetts, residence believe to have been connected to Boston Marathon bombings suspect Dzhokhar Tsarnaev, New Bedford Police Lt. Robert Richard said.

[Updated 8:32 p.m. ET] FBI agents interviewed Tamerlan Tsarnaev - the 26-year-old Boston Marathon bombing suspect killed following a gunfight with authorities overnight - in 2011 at the request of foreign government, an FBI official said Friday. The other government - who the official would not name - suspected that Tsarnaev may have ties to extremist groups. The FBI investigated, including interviewing Tsarnaev, but the matter was closed after no derogatory information was found, according to the official.

[Updated 8:13 p.m. ET] A person believed to be Dzhokar Tsarnaev, the suspect in this week's Boston Marathon bombings, is cornered on a boat in a yard in Watertown, Massachusetts, law enforcement officials said.

[Updated 8:05 p.m. ET] Authorities believe the person they've engaged in Watertown, Massachusetts, is Dzhokar Tsarnaev, a suspect in this week's deadly Boston Marathon bombings, a law enforcement official told CNN. CNN crews reported hearing multiple explosions near the site where authorities have engaged the suspect.

[Updated 7:46 p.m. ET] As many as a dozen people were being moved away from the scene of intense police activity in Watertown, Massachusetts, including a young girl being carried in a police officer's arms, CNN's David Fitzpatrick reported.

[Updated 7:34 p.m. ET] Authorities have engaged the possible remaining suspect in the Boston Marathon bombings in Watertown, Massachusetts, a senior federal law enforcement official said.

[Updated 7:14 p.m. ET] The Boston Police Department tweeted that there are "police operations" on Franklin Street in Watertown, Massachusetts. CNN crew at the scene heard gunshots and saw several law enforcement vehicles race toward the scene.

Heavy police presence in area of Franklin St in Watertown. Residents remain inside.

[Updated 6:26 p.m. ET] A "stay indoors" order has been lifted in Boston while the manhunt continues for the remaining suspect in Monday's Boston Marathon bombings.

Authorities believe that 19-year-old Dzhokar Tsarnaev is likely still in Massachusetts, state police spokesman Col. Timothy Alben said Friday.

"He's a very violent and dangerous person," Alben said in a news conference Friday. "We do not have an apprehension of our suspect this afternoon, but we will have one."

Massachusetts state troopers will remain in Watertown, where the suspects engaged in an overnight gunfight with police, for at least three more days, Alben said.

Some 200 rounds" of gunfire were exchanged during the firefight, Gov. Deval Patrick added.

The area's public transit system, known as the T, has reopened Friday night after being shut down most of the day, Patrick said.

"We can return to living our lives."

[Updated 5:54 p.m. ET] Fifteen patients wounded in this week's marathon bombings remained hospitalized Friday at Boston Medical Center, the hospital said. One of those patients is in critical condition, 10 are in serious condition, and four are in fair condition. The Boston hospital - one of several in the area treating the wounded - received 23 patients tied to Monday's blasts overall.

Eleven patients wounded in this week's Boston Marathon bombings remain at Boston's Brigham and Women's Hospital - down from the more than 30 patients total the hospital has treated, and not including those treated at its affiliate Faulkner Hospital - the hospital said Friday. One of those patients is in critical condition. Several other Boston-area hospitals are still treating injured patients as well.

[Updated 5:12 p.m. ET] Anzor Tsarnaev - father of Boston bombings suspects Dzhokar Tsarnaev and Tamerlan Tsarnaev - who earlier told Russian national TV network Zvezda that he believed his sons were "framed" tells CNN from Dagestan that he was questioned Friday by Russian security services and then released.

[Updated 4:16 p.m. ET] Connecticut State Police have issued a new vehicle lookout alert in connection with the probe in neighboring Massachusetts: They say Boston-area authorities are looking for a 1995 gray Honda Odyssey with Massachusetts registration 93NN73. A suspect in the Boston Marathon bombing might be in that vehicle, police said.

Connecticut police have issued a few vehicle alerts today, saying they've been monitoring information coming from investigators across the state line.

"Someone framed them," Anzor Tsarnaev said during the interview Friday in Russia's North Caucasus republic of Dagestan. "I don't know exactly who did it. But someone did. And being cowards, they shot the boy (Tamerlan) dead. There are cops like this."

Anzor Tsarnaev said that whoever was behind the Boston Marathon bombings "is a bastard."

He said he was trying to get in touch with his family members in Canada and the United States, but he can't get through by phone.

"Those are my kids, you understand? Maybe he will be shot dead, too," he told Zvezda. "They will say, well, he had weapons. Kids with weapons? ... They should arrest him maybe and bring him, but alive. Alive. And justice should decide who's right and who's guilty."

Noting that he had lived in the United States, Zvezda asked him whether he ever had problems with the U.S. justice system.

'No, never. But I just didn't face it ever. So can I know about the justice there? I didn't have any problems," he said.

[Updated 3:53 p.m. ET] Boston police say the second vehicle they were looking for today, a vehicle with Massachusetts plate 116 GC7, has been found.

[Updated 3:43 p.m. ET] "Investigators are recovering a significant amount of homemade explosives" from last night's Watertown scenes, and ‚Äúthere is no proof yet of accomplices," Massachusetts State Police Spokesman David Procopio said, according to CNN's Susan Candiotti.

Police had said that the suspects were throwing explosives at them during last night's pursuit in the Watertown area.

[Updated 3:27 p.m. ET] Amtrak service between Boston and New York has been suspended, police say:

#CommunityAlert: AMTRAK service between Boston and New York suspended pending further notice.

[Updated 2:30 p.m. ET] Two students at the University of Massachusetts-Dartmouth, where Dzhokar Tsarnaev was registered, told CNN that they saw him on campus this week, after Monday's Boston Marathon bombing, CNN's Chris Lawrence reported.

Also Friday, a helicopter with a number of law enforcement personnel landed on campus, Lawrence reported.

The school ordered an evacuation of its campus on Friday. The school is located 65 miles south of Cambridge, just west of New Bedford.

[Updated 2:04 p.m. ET] Connecticut State Police have issued an alert for another vehicle, saying a wanted suspect in the Boston Marathon attack now could be in a 1999 green Honda Civic with Massachusetts license plate number 116 GC7. The CSP cited Boston authorities.

Connecticut police issued a similar alert earlier today for a different vehicle; that vehicle eventually was found unoccupied Friday in the Boston area, Boston police said.

[Updated 1:51 p.m. ET] More details on the Tsarnaev brothers:

Dzhokhar Tsarnaev, 19, the Boston Marathon attack suspect now at large, came to the United States on July 1, 2002, at age 8 on a tourist visa, a federal source said. While here, he sought asylum and became a citizen on September 11, 2012.

His older brother Tamerlan Tsarnaev, who was killed in a shootout with police overnight, came to the United States four years after his brother, on Sept. 6, 2006, at the age of 20, the source said. He came legally but was not naturalized. He was a green card holder and in the country lawfully.

The violence began late Thursday with the robbery of a convenience store, according to Timothy Alben, superintendent of the Massachusetts state police. Soon after, in Cambridge, across the Charles River from Boston, Massachusetts Institute of Technology police officer Sean Collier was fatally shot while he sat in his car, the Suffolk County District Attorney's Office said in a statement.

Police believe the Boston Marathon bombing suspects were responsible for the shooting.

The two suspects, according to authorities, then hijacked a vehicle at gunpoint in Cambridge, telling the driver that they are the marathon bombers, a law enforcement source told CNN's Joe Johns. At some point, apparently at a gas station, the source said, the driver escaped.

Police, who were tracking the vehicle using its built-in GPS system, picked up the chase in Watertown. The pursuit went into a residential neighborhood, with the suspects throwing explosives at the police. A firefight erupted and ultimately one suspect - later identified as Tamerlan Tsarnaev - got out of the car. Police shot him, and his brother ran over him as he drove away, according to the source.

Earlier, there had been reports that Dzhokar Tsarnaev escaped on foot instead of by vehicle.

A source briefed on the investigation said Tamerlan Tsarnaev was wearing explosives and an explosive trigger. He died later at Beth Israel Hospital.

Richard H. Donohue Jr., 33, a three-year veteran of the transit system police force, was shot and wounded in the incident and taken to a hospital, a transit police spokesman said Friday. The officer's condition was not immediately known.

[Updated 12:45 p.m. ET] Police are continuing to run down new leads and go door to door in Watertown in the Boston Marathon terror attack investigation, said Timothy Alben, superintendent of the Massachusetts state police. He told reporters that law enforcement will conduct a controlled blast later in Cambridge, an indication that police found suspected explosives.

[Updated 12:44 p.m. ET] Massachusetts Gov. Deval Patrick says his request for people in the Boston area to stay indoors remains in effect for now. "We know what an inconvenience it is, in Watertown and Cambridge in particular ... but it‚Äôs been enormously helpful ‚Ä¶ to law enforcement.‚ÄĚ

[Updated 12:30 p.m. ET] The Kyrgyz government said Friday that the two Boston Marathon suspects moved from Kyrgyzstan 12 years ago to the Russian region of Dagestan, from where the Tsarnaev family emigrated to the United States.

"Given that the suspects left the Republic at the ages of 8 and 15, the State Committee for National Security of Kyrgyzstan considers it inappropriate to link them to Kyrgyzstan," it said.

[Updated 12:25 p.m. ET] Dzhokar Tsarnaev, 19, was registered at the University of Massachusetts-Dartmouth, which ordered its campus evacuated on Friday. The school is located 65 miles south of Cambridge, just west of New Bedford.

"UMass Dartmouth has learned that a person being sought in connection with the Boston Marathon bombing has been identified as a student registered at UMass Dartmouth," the school said in a news release. "The campus is closed. Individuals on campus should shelter in place unless instructed otherwise."

The tweets included one at 1:43 a.m. Wednesday that said, "I'm a stress free kind of guy."

On Monday at 8:04 p.m. - hours after the bombings - he tweeted a lyric from a song that rapper Jay-Z has sampled: "Ain't no love in the heart of the city, stay safe people."

On Tuesday shortly after midnight he tweeted, "There are people that know the truth but stay silent & there are people that speak the truth but we don't hear them cuz they're the minority."

[Updated 11:55 a.m. ET] The uncle of the Tsarnaev brothers told reporters outside his home in Montgomery County, Maryland, this morning that his family is "ashamed" to be related to the suspects.

Ruslan Tsarni said the 19-year-old suspect still on the run "has put a shame on our family, a shame on the entire ethnicity." Tsarni urged his nephew to turn himself in.

He said anyone capable of committing such a crime are "losers."

[Updated 11:20 a.m. ET] U.S. Secretary of State John Kerry praised law enforcement in their hunt for the Boston Marathon attack suspects.

"I think it is fair to say this entire week we have been in pretty direct confrontation with evil," he said. "In the past few days we have seen the best and we have seen the worst of human behavior and it is the best that all of us really want to focus on."

[Updated 10:55 a.m. ET] Taxi service in Boston has been restored, police said. The service had been suspended earlier today because of the manhunt in the Boston bombings case.

[Updated 10:50 a.m. ET] Another flurry of police activity is happening in Watertown, the Massachusetts community where police say one suspect was killed and another was being sought.

Police are asking reporters to move back - and stay down - as a number of other officers are drawing guns in a certain area, CNN's Deborah Feyerick reports from Watertown.

[Updated 10:41 a.m. ET] Connecticut State Police say that a vehicle that might be connected to a suspect in the Boston Marathon attack has been recovered in the Boston area. The vehicle is a gray Honda CR-V with Massachusetts plate 316 ES9.

Connecticut police earlier had issued a lookout notice for the vehicle.

This is what Boston police had to say about the vehicle earlier, on Twitter: "Police seeking MA Plate: 316-ES9, ‚Äô99 Honda CRV, Color – Gray. Possible suspect car. Do not approach."

[Updated 10:29 a.m. ET] A high school friend of Dzhokar Tsarnaev, the suspect who Boston police say still is at large, is recalling what he remembers about him.

Eric Mercado told CNN that he went to Cambridge Rindge & Latin, a public high school, with Dzhokar Tsarnaev, 19. Both graduated, he said.

"We hung out; we partied; we were good high school friends," Machado told CNN. "We're all, like, in shock. We don't really understand. There were no telltale signs of any kind of malicious behavior from Dzhokar. It's all coming as a shock, really."

[Updated 10:24 a.m. ET] More background on the brothers that several sources tell CNN are the suspects involved in Thursday night's shootings and police chase and Monday's Boston Marathon bombings:

The Tsarnaev brothers were Kyrgyz passport holders, and used those passports when applying for green cards in the United States, an official in the central Asian republic of Kyrgyzstan said, according to CNN's Ivan Watson.

This doesn't mean they were born in Kyrgyzstan or that their family were Kyrgyz natives. Many Caucasus refugees received passports or refugee status in surrounding countries.

[Updated 10:14 a.m. ET] Some background on the brothers that several sources tell CNN are the suspects involved in Thursday night's shootings and police chase and Monday's Boston Marathon bombings:

Dzhokar Tsarnaev, 19, the Boston Marathon attack suspect now at large, came to the United States as a tourist in the early 2000s and asked for asylum while he was here, a federal source said. He was naturalized last year. Tamerlan, the 26-year-old brother who was killed overnight, came "a few years later" and was a green-card holder, not a naturalized citizen, the source said, according to CNN's Mike Ahlers.

[Updated 10:02 a.m. ET] We now have the name of he Massachusetts Institute of Technology police officer who was killed Thursday night - he was Sean Collier, 26, of Somerville, Massachusetts, according to the Middlesex district attorney‚Äôs office.

[Updated 9:48 a.m. ET] An aquatic director at Harvard University told CNN that he hired Dzhokar Tsarnaev as a lifeguard more than two years ago, but hasn't seen him for more than a year.

"He seemed like a very quiet, unassuming young man," the aquatic director, George McMasters, told CNN Friday morning. "He showed up on time, watched the water, rotated from position to position fine, got along well with students and swimmers there at the pool."

[Updated 9:31 a.m. ET] The Boston bombings suspect who was killed in a confrontation with police overnight in the Boston area was wearing explosives and an explosive trigger when his body was recovered, a source briefed on the investigation says, according to CNN's Deborah Feyerick.

Several sources tell CNN that the dead suspect has been identified as Tamerlan Tsarnaev, 26, and the one still being sought in Watertown is Dzhokar Tsarnaev, 19.

Police have publicly said that the dead suspect is the man that the FBI previously identified as "Suspect No. 1" in the Boston Marathon bombings. They also have said publicly that the suspect that they chased and last saw in Watertown overnight is the man that the FBI said was "Suspect No. 2"; Boston police also have said that they're looking for Dzhokar Tsarnaev.

[Updated 9:16 a.m. ET] The brothers suspected in the Boston Marathon attack haven't been connected to the Russian region of Chechnya for many years, the Chechen president's office said, according to the Interfax news agency.

The Tsarnaev family years ago moved out of Chechnya to another Russian region, lived some time in Kazakhstan, and then went to the United States where the family members received a residence permit, the office said.

"Therefore, the individuals concerned did not live as adults in Chechnya," said Alvi Kamirov, press secretary for Chechnya's president.

[Updated 9:01 a.m. ET] Boston police have now named a suspect that authorities have been seeking this morning. "Suspect identified as 19 year-old Dzhokar Tsarnaev of Cambridge. Suspect considered armed & dangerous," Boston police said on Twitter.

Dzhokar Tsarnaev is a Boston Marathon bombings suspect that police are looking for in Watertown following a chase overnight and shootings overnight, several sources told CNN earlier Friday.

Tamerlan Tsarnaev, 26, was the suspect who was killed during a police confrontation overnight, those same sources told CNN.

Police have said that the man identified by the FBI as "Suspect No. 1" in the Boston Marathon bombings was killed in the police confrontation. The man identified by the FBI as "Suspect No. 2" is on the loose, last seen in Watertown, police said.

[Updated 8:52 a.m. ET] A recap of the developments that began Thursday night:

The violence began late Thursday with the robbery of a convenience store, not long after the FBI released images of two suspects in the Boston Marathon bombings, Massachusetts State Police spokesman Col. Timothy Alben said.

Soon after, in Cambridge, across the Charles River from Boston, a Massachusetts Institute of Technology police officer was fatally shot while he sat in his car, the Suffolk County District Attorney's Office said in statement. Police believe the bombing suspects were responsible for the shooting.

The same two suspects, according to authorities, then hijacked a car at gunpoint in Cambridge. They released the driver a half-hour later at a gas station. As police picked up the chase, the car's occupants threw explosives out the windows and shot at officers, according to the district attorney's office.

Officers fired back, wounding one of the men, possibly the person identified by the FBI as "Suspect No. 1." The man died at Beth Israel Hospital. He had bullet wounds and injuries from an explosion, according to officials. The second man apparently escaped.

Richard H. Donohue Jr., 33, a three-year veteran of the transit system police force, was shot and wounded in the incident and taken to a hospital, a transit police spokesman said Friday. The officer's condition was not immediately known.

[Correction at 1:36 p.m. ET] The 8:52 a.m. entry above initially said that the second man apparently escaped on foot. "On foot" has been removed, as that part no longer appears to be the case.

[Updated 8:44 a.m. ET] Police activity in Watertown - where authorities believe they last saw "Suspect No. 2" during a chase overnight - seems to be picking up, CNN's Deborah Feyerick reports from the community. A helicopter is hovering over a building, and reporters are being asked to move back from where they were.

[Updated 8:30 a.m. ET] The FAA has ordered a 3.5-nautical-mile temporary flight restriction over Boston "to provide a safe environment for law enforcement activities." The restriction is from surface to 3,000 feet, according to the FAA website.

[Updated 8:21 a.m. ET] ‚ÄúAll taxi service in the city of Boston has been suspended pending further notice,‚ÄĚ Boston Police said on its official Twitter account.

This meshes with authorities' request that all of Boston and many of its suburbs stay indoors - with doors locked - until further notice. All public transportation in Boston already has been suspended, schools are closed, and Amtrak service from Boston to Providence, Rhode Island, also has been suspended.

[Updated 8:16 a.m. ET] The Boston-area transit police officer who was shot and wounded overnight is Richard H. Donohue Jr., 33, a three-year veteran of the force, a transit police spokesman said Friday. Donohue was shot during the manhunt for the Boston Marathon bombing suspects.

[Updated 8:10 a.m. ET] The suspects involved in the Boston bombings are brothers originally from the Russian Caucasus and had moved to Kazakhstan at a young age before coming to the United States several years ago, according to a source briefed on the investigation, CNN's Deborah Feyerick reported.

The older of the two brothers had the first name Tamerlan, had studied at Bunker Hill Community College, and wanted to become a engineer, the source said. He then took a year off to train as a boxer, according to the source.

The source said that a posting on a social media site in his name included the comments: "I don't have a single American friend. I don't understand them."

The source added that it should not be assumed that either brother was radicalized because of their Chechen origins.

[Updated 8:07 a.m. ET] "All of Boston" should shelter in place, Massachusetts Gov. Deval Patrick has just told reporters. The same applies to suburbs of Watertown, Newton, Belmont, Cambridge and Waltham, he said.

By shelter in place, Deval said he meant people should stay indoors, keep doors locked and not answer doors for anyone except for police.

Patrick also has confirmed to reporters that one Boston bombings suspect is dead and the other is on the loose.

He added:

- An Massachusetts Bay Transportation Authority officer was "seriously wounded" and is in surgery right now.- An MIT security officer was killed.

[Updated 7:59 a.m. ET] A recap of what authorities are telling Boston-area residents to do: Police ordered businesses in the suburb of Watertown and nearby communities to stay closed and told residents to stay inside and answer the door for no one but authorities.

The subway and Amtrak train systems have been shut down. Every Boston area school is closed.

[Updated 7:39 a.m. ET] The suspects in the Boston Marathon terror attack were brothers, a terrorism expert briefed on the investigation said, according to CNN's Deborah Feyerick.

[Updated 7:34 a.m. ET] One of two suspects in the Boston Marathon bombing - the man police were looking for Friday morning - has a name that is common among people from the North Caucasus, a source with knowledge of the investigation said Friday. That region includes the breakaway Russian republic of Chechnya.

Earlier Friday, The Associated Press reported that the two suspects in the Boston Marathon bombings are brothers believed to be from an area near Chechnya.

[Updated 7:32 a.m. ET] Police in the Boston-area community of Cambridge say the public should "clear area of Norfolk Street in Cambridge." "Ongoing investigation. Potentially dangerous," Cambridge police said on Twitter.

[Updated 7:29 a.m. ET] Boston police have given a heads-up to the public: They'll be conducting a "controlled explosion" - basically neutralizing a suspicious object - near the area of Commonwealth Avenue and Charlesgate.

[Updated 7:28 a.m. ET] Recapping what a doctor at Boston's Beth Israel told reporters this morning about the death of the man police believe is "Suspect No. 1" in the Boston bombings: He had bullet wounds and injuries from an explosion, the doctor said.

The doctor said he didn't know the cause of death, and he didn't know what the explosion was. The suspect was pronounced dead after unsuccessful attempts to reanimate him, a hospital spokesman said.

Police said the man believed to be "Suspect No. 1" was wounded in Watertown near Boston following a pursuit. That pursuit came about after the fatal shooting of a Massachusetts Institute of Technology police officer, authorities said.

[Updated 7:03 a.m. ET] The Associated Press has reported that the two suspects in the Boston Marathon bombings are brothers believed to be from an area near Chechnya.

[Updated 6:48 a.m. ET] More transportation options in an out of Boston are being shut down as police look for "suspect No. 2" in the Boston Marathon bombings. Amtrak train service between Providence, Rhode Island, and Boston has been suspended, Amtrak said Friday.

The FBI on Thursday released this image of what it called "suspect No. 2" in Monday's Boston Marathon bombings. Authorities said Friday that they're looking for him in the Boston suburb of Watertown.

[Updated 6:36 a.m. ET] A number of universities in the Boston area have been closed because of the manhunt for a suspect in the Boston Marathon terror attack, school officials said. They include Harvard University, the Massachusetts Institute of Technology, Boston University, Emerson College, and Boston College.

[Updated 6:23 a.m. ET] A person who was shot and killed in the Boston Marathon terror attack manhunt is believed to have had explosives on his body, a law enforcement official with knowledge of the investigation said Friday.

[Updated 6:19 a.m. ET] Here's some more details about the public-transportation shutdown in Boston: All Massachusetts Bay Transportation Authority service is suspended at the request of the police, Joe Pesaturo, the authority's public information officer, said Friday. This includes bus, subway, commuter rail, and ferry routes in the Boston area.

This comes as police say they're continuing to hunt down one of the suspects in Monday's Boston Marathon terror attack.

[Updated 5:59 a.m. ET] "Harvard University is closed due to public safety concerns. Please continue to watch this page for updates," the university announced on its website.

[Updated 5:43 a.m. ET]: Mass transit in Boston has been suspended at the request of the police, says Joe Pesaturo, spokesman for the Massachusetts Bay Transportation Authority.

[Updated 5:37 a.m. ET]: Boston Police, via its official Twitter account, says businesses near 480 Arsenal Street in Watertown, Massachusetts, are closed until further notice. Employees are also instructed to stay home.

[Updated 5:20 a.m. ET]: MIT cancels Friday's classes, according to a letter from Israel Ruiz, the school's executive vice president and treasurer, and school Chancellor Eric Grimson.

"MIT suffered a tragedy last night: an MIT Police officer was shot and killed on our campus in the line of duty," says the letter, addressed to the MIT community. "While the circumstances around the officer's death remain the subject of an active investigation, what is certain is that the officer gave his life to defend the peace of our campus. His sacrifice will never be forgotten by the Institute. We are thinking now of his family, and our hearts are heavy. In consultation with faculty chair Sam Allen, we have decided to cancel classes today (Friday). All employees are encouraged to use their best judgment about whether they are prepared to come in to work today: any absence today will be considered excused."

[Updated 4:45 a.m. ET]: One of the suspects believed to have planted bombs at the Boston Marathon is dead after a shootout with police, a police spokesman said.

The FBI on Thursday released this image of who it called "suspect No. 1" the Boston Marathon bombings. On Friday, police said he was killed in a Boston-area shootout with police.

[Updated 4:21 a.m. ET]: A suspect on the loose in Watertown, Massachusetts, matches the description of Suspect 2 - a man pictured wearing a white cap - wanted in connection with the bombings at the Boston Marathon on Monday, police said early Friday.

[Updated 3:54 a.m. ET]: Massachusetts State Police, via Twitter: "Police will be going door by door, street by street, in and around Watertown. Police will be clearly identified. It is a fluid situation."

[Updated at 3:48 a.m. ET]: Massachusetts State Police, on its official Twitter feed, warns Watertown residents to stay in their homes and to not answer the door "unless it is an identified police officer." "If any concerns about someone at door, call 911 immediately. Repeat–Do not answer door, stay away from windows, keep doors locked," the state police says in another tweet.

[Updated 2:40 a.m. ET]: Massachusetts State Police spokesperson Dave Procopio said that they believe multiple possible explosive devices were used against police tonight during this incident at Watertown. It was unclear if the incident, which followed a police chase of a stolen vehicle, was related to the shooting on the MIT campus or any other incident in the Boston area.

[Updated 2:31 a.m. ET]: FBI spokesman Martin Feely tells CNN's Susan Candiotti: "We are engaged with our partners trying to determine if there is a connection." CNN's Drew Griffin, who is on the scene in Watertown, Massachusetts, said FBI agents are on the scene.

[Updated 2:21 a.m. ET]: MIT releases statement on shooting death of campus police officer:¬†"MIT is heartbroken by the news that an MIT Police officer was shot and killed in the line of duty on Thursday night on campus, near Building 32 (the Stata Center). Our thoughts are now with the family." http://bit.ly/15lcg2r

[Updated 2:19 a.m. ET]: Boston Police Department's official Twitter feed says "there is an active incident ongoing in Watertown. Residents in that area are advised to remain in their homes. More details when available."

[Updated 2:07 a.m. ET]: CNN's Gabe Ramirez on the scene in Watertown, Massachusetts, says that authorities are ordering people in the area to shut off their cell phones.

[Updated 1:49 a.m. ET]: At least one person was arrested in Watertown, Massachusetts early Friday morning, stripped naked before being taken in custody, CNN photojournalist Gabe Ramirez observed. It is unclear if this arrest was related to the shooting at Massachusetts Institute of Technology campus or any other incident in Boston the area.

[Updated 1:23 a.m. ET]:¬† Dozens of police have rushed to an area of Watertown, Massachusetts, just over two miles from Cambridge, said CNN's Drew Griffin, who is near the scene. A "very large event has taken place," Griffin said. There were reports that explosives were involved.

[Posted at 12:45 a.m. ET]: A university police officer has died after being shot on the Massachusetts Institute of Technology campus in Cambridge late Thursday, state police spokesman Lt. Mark Riley said.¬†The MIT officer was responding to a disturbance when he was shot, according to the state district attorney's office. He sustained "multiple gunshot wounds."

State police and the FBI were called in after the shooting and found the campus policeman near Building 32 on MIT's campus. He was taken to Massachusetts General Hospital, where he was pronounced dead, the district attorney's office said. Dozens of officers surrounded and cordoned off the building, known as the Stata Center, which houses computer science laboratories as well as the department of linguistics and philosophy, according to MIT's website.

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